Plants as effective bioindicators for heavy metal pollution monitoring

This study investigated the bioindicator potential of Amaranthus retroflexus L., Plantago lanceolata L., Rumex acetosa L., and Trifolium pratense L. including the use of Lolium multiflorum L. as a reference species, for heavy metal pollution monitoring, in particular Zinc (Zn), Cadmium (Cd), Nickel (Ni), and Lead (Pb). Controlled heavy metal contamination was applied through irrigation with metal nitrate solutions two levels of contamination (low and high). The study also focused on analyzing heavy metals concentration in plant tissues and related physiological responses. Distinct physiological responses to heavy metal stress were observed among the investigated species, highlighting unique variations in their reactions. Hydrogen peroxide, malondialdehyde content, and enzymatic activities emerged as reliable indicators of plant stress induced by heavy metal solutions. P. lanceolata displayed elevated Zn concentrations in both roots and leaves (3271 ± 337 and 4956 ± 82 mg kg^-1). For Pb, L. multiflorum and P. lanceolata showed highest root concentrations (2964 ± 937 and 1605 ± 289 mg kg^-1), while R. acetosa had higher leaf concentration (1957 ± 147 mg kg^-1). For Ni, L. multiflorum had the highest root concentration (1148 ± 93 mg kg^-1), and P. lanceolata exhibited the highest leaf concentration (2492 ± 28 mg kg^-1). P. lanceolata consistently demonstrated the highest Cd concentrations in both roots (126 ± 21 mg kg^-1) and leaves (163 ± 12 mg kg^-1). These results provide valuable insights for selecting effective bioindicator species to establish control strategies for heavy metal pollution.